The present invention relates to a method of fabricating a semiconductor device, and more particularly to a wire-bonding method for a semiconductor device.
In the method for manufacturing a semiconductor device, a wire-bonding process to electrically connect bonding pads on the semiconductor pellet and inner leads using bonding wires can be said to be an extremely important process. When carrying out such a wire-bonding, it is required to input bonding positional coordinates to the bonding apparatus. Typical methods of inputting bonding position coordinates which have been conducted in the art will be now described.
(1) Method of preparing a ROM
This method is featured by writing positional coordinate data into a PROM to deliver the data thus written to the bonding apparatus, and is implemented in accordance with the following procedure.
(a) An operator reads bonding positional coordinate data, i.e., positional coordinates of the bonding pads and positional coordinates of internal junctions of lead frames from the plan or design drawing of the semiconductor pellet and the lead frame.
(b) Coordinate values which have been read in a predetermined format are written using a PROM writer.
(c) The PROM having been written is set at the bonding apparatus to confirm the bonding positions on the bonding apparatus.
(d) If there is any dislocation in the bonding positions, the coordinate value of question is corrected to repeat the procedure from the process (b). When correction is made by parallelly moving the bonding positions in a whole scale, a digital switch provided on the bonding apparatus is operated to thereby set a quantity parallelly moved.
(2) Method of carrying out teaching work
According to this method, a teaching work is conducted to display an object of wire-bonding using a TV camera with it being locally enlarged, whereby an operator instructs positional coordinates to be subjected to bonding while observing a pictorial image on the monitor. This method is carried out in accordance with the following procedure.
(a) Movement adjustment of the XY stage of the bonding apparatus is made so that a point on an object which is to be the start point of the wire No. 1 is displayed at the central position of the monitor pictorial image. When the adjustment is completed, a predetermined input switch is operated to thereby store the coordinate values of the start point into the RAM provided in the bonding apparatus. This is so called "teaching work".
(b) Subsequently, similar teaching work is conducted connection with the coordinate values of the point which is to be the terminating point of the wire No. 1, thereafter to store the coordinate values into the RAM.
(c) The above-mentioned procedures (a) and (b) are successively conducted in connection with the entire
(d) Finally, the procedures (a) and (b) are conducted a second time in connection with the wires to be subjected to correction or alternation, thus to perform correction or alternation. When there is a need to parallelly move the bonding positions in a whole manner to make correction, it is sufficient to set a quantity parallelly moved in accordance with the same teaching work as that indicated by the procedure (a).
However, the drawbacks with the above-mentioned methods are as follows.
(1) The drawbacks with the method of preparing ROM.
An operator must manually carry out all of the work including the work for reading coordinate values from the plan, the work for writing the coordinate values into PROM, and the work for correcting the coordinate values. These works are very troublesome, with the result that not only much labor and time are spent, but also an error is likely to occur.
(2) The drawbacks with the method of carrying out the teaching work.
This method allows the load of the work to be somewhat reduced as compared to the method described in the above-mentioned paragraph (1) in that it is not required for an operator to directly handle numerical values. However, the teaching work can be still said to be the work in which much labor and time are spent and an error is likely to occur. For example, since the pictorial image on the monitor is obtained by locally enlarging an object of wire-bonding using a TV camera, the visual field is narrow and it is very difficult for an operator to recognize which portion of the entirety of the object of wire-bonding is occupied by the pictorial image presently displayed. For this reason, there likely occurs an error such that teaching is erroneously conducted in connection with the adjacent bonding pads or adjacent leads.
As just described above, the conventional wire-bonding methods have the drawbacks that it takes much labor and time in the work for inputting bonding positional coordinates, resulting in high possibility that the work is erroneously conducted.